Peocess of makijjg phokphobic acid and cyanamide



T. F. B'AILY PROCE s r Sept. 22, 1931 s o MAKING PHOSPHOHIC ACID AND CYANAIIDE Re. 18,198

Original Filed Feb. 5. 1929 co PHOSPHATE Rock CARBON (002 0TH:& REDUCING AGENT) co P m De ER Reoqcms- FURNACE Lpqulo P Ca. 14 1 C2 Am g;

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UNITED STATES PATENT OFFICE.

'rnannnus r. BAILY; or ALLIANCE, 01110 spouses or MAKING rnosrnomo son) an cxaummn Original No. 1,775,802, dated September 16, 1930, Serial No. 387,573, fled February 5, 1929. Application for reissue filed May 21, 1931. Serial No. 539,119.

The invention relates to the production of phosphoric acid and calcium cyanamide and more particularly to a combined electric furnace process of producing the phosphoric acid and cyanamide.

It is not known that anyone has ever made two fertilizer constituents, i. e. phosphoric acid and fixed nitrogen from phosphate rock as a raw material. All present operating processes for producing, by electric furnace method, phosphoric acid and cyanamide, do not include an inter-relation in producing these two constituents. 'In-all electric furnace methods for producing phosphoric acid :1; from. phosphate rock silica is added to the calcium oxide left from the rock upon elimination ofthe phosphorus, and the resultant "calcium silica slag, or calcium silicate, is

worthless except for filling or road purposes; and all calcium cyanamide, produced by electric furnace process, is made from limestone, or lime, and carbon, and the nitrogen for nitriding the carbide is produced by the freezing of air.

he present invention. contemplates the combined production of phosphoric acid and calcium cyanamide by reducing a charge of phosphate rock, in an electric furnace, in the presence of carbon, the phosphorus released '30 b the reducing operation being recovered as p osphoric acid, the resultant slag from the phosphorus reducing operation eing converted to calcium carbide, nitro en being passed over the calcium carbide while maintained at a sufiicient temperature to produce calcium cyanamide.

The object of the improvement is to provide a process and apparatus whereby a charge such as phosphate rock and a re ucing agent such as coke may be placed in an electric furnace, the CO gas, or other carrier, and volatile phosphorus being withdrawn fromthe furnace and condensed, the CO gas being'freed from the phosphorus which is liquefied in the condenser and passed to an oxidizing furnace to which air is admitted, preferably under pressure. p

The phosphoric acid and nitrogen produced, by this oxidizing process are then passed through a cooler and then to a prephosphate rock cipitator in which the phosphoric acid is separated from the nitrogen and withdrawn.

The calcium slag resulting from the phosphorus reduction in the electric furnace is converted, while still in the furnace, into calcium carbide and may be flowed from the furnace to a cooler and then crushed and passed into a nitrogen fixation furnace.

The nitrogen'that has been freed in the phosphorus oxidizing operation is admitted to this fixation furnace and passed over the crushed or ground calcium carbide at a red heat, forming calcium 0 anamide.

In the drawing, the fi gure is a diagrammatic view of apparatus which may be used for carrying out the im roved process.

Similar numerals re cr*tofs1milar throughout the drawing.

An electric furnace of any suitable type is indlcated generally at 10. For the purpose of the invention this furnace may be of 5,000 kw. capacity and may be charged with fine and coke breeze in substantially the proportions of one and one-half tons of phosp ate rock to nine-tenths of a ton of coke breeze per hour.

The charge may be fed continuouslyinto the furnace, in the proportions named, so as to maintain a constant temperature throughout the various zones of the furnace and to insure an even flow of phosphorus va or and calcium carbide from the furnace. is also tends .to kee the roofof the furnace sufliciently cool or operating purposes.

The carbon monoxide roduced in the reduction of the charge in t e furnace, amounting to about 1450 pounds of CO, in which about 400 pounds of reduced phosphorus in volatile form is entrained, is removed from parts the furnace through a duct 11 and carried to I a condenser 12, preferably water cooled, where the phosphorus is condensed to a liquid, the carbon monoxide thus freed being removed through the pipe 13 and made available for any practicaluse, such as for heating or preheatlng the charge ofraw material.

The liquid phosphorus is then conducted from the condenser through a duct 14 to an oxidizing furnace or water cooled oxidizing chamber 15 into which air is blown, as by a V '5. The combined of producing phos horic acid an calcium cyanamide whio consists in reducing hosphate rock with carbon, withdrawing C gas and volatile phosphorus therefrom, condensing the volatile ph horus and removing it from the CO, adding air to the condensed phosphorus and cooling the same, roducing phosphoric acid and nltrogen an passing the nitrogen thus obtained over the calcium carbide resulting fromthe reducing operation, the calcium carbide being maintained at a sufiicient temperature to produce calcium cyanamide.

6. The combined process of producing phosphoric acid an calcium 0 anamide which consists in reducing (phosp ate rock with carbon, withdrawing C gas and volatile phosphorus therefrom, condensing the volatile phosphorus and removing it from the CO, addin air to the condensed phosphorus and coo mg the same, producing phosphoric acid and nitrogen, crushing the calcium carbide resulting from the reducing operation and passing the freed nitrogen over the calcium carbide, the calcium carbide being maintained at a suflicient temperature to produce calcium cyanamide.

7. The combined rocess of producing phosphoric acid an calcium 0 anamide which consists in reducing hosp ate rock with carbon, withdrawing C8 gas and volatile phosphorus therefrom, condensing the volatile phosphorus and removing it from the CO, addm air to the condensed phosphorus and coo mg the same, producin phosphoric acid and nitrogen, crushing t e calcium carbide resulting from the reducing operation, and reheating the calcium carbide in the presence of the nitrogen, producing calcium cyanamide.

8. The combined process of producing phosphoric acid and calcium cyanamide which consists in reducing phosphate rock with carbon, withdrawing CO gas and volatile phosphorus therefrom, condensing the volatile phosphorus and removing it from the CO, addin air to the condensed phosphorus and coo ng the same, producing phosphoric acid and nitrogen, cooling the calcium carbide resultin from the reducing operation, crushing t e calcium carbide, and reheating the calcium carbide in the presence o; the nitrogen producing calcium cyanam- 1 e.

9. The combined rocess of producing phosphoric acid and calcium c anamide which consists in reducing hosp ate rock with carbon, withdrawing C gas and volatile phosphorus therefrom, condensing 'the volatile p osphorus and removing it from the CO, oxidizing the condensed phosphorus with air, preciipitating the same producing phosphoric aci and freeing the nitrogen and passing the nitrogen thus obtained over the calcium carbide resulting from the reducing operation, the calcium carbide being maintained at a suflicient temperature to produce calcium cyanamide.

10. The combined process. of producing phosphoric acid and calcium cyanamide which consists in reducing ghosphate rock with carbon, withdrawing C gas and volatile phosphorus therefrom, condensing the tile phosphorus therefrom, condensing the volatile phosphorus and removing it from the CO, oxidizing the condensed phosphorus with air, precipitating the same producing phosphoric acid and freeing the nitrogen,

crushing the calcium carbide resultingfrom 1 the reducing operation, and reheating the calcium carbide in the presence of the nitrogen, producing calcium cyanamide.

12. The combined process of producing which consists in reducing phosphate rock with carbon, withdrawing CO gas and volatile phosphorus therefrom, condensing the volatile phosphorus and removin it from the CO, oxidizing the condensed phosphorus with air, precipitating the same producing phosphoric acid and freeing the nitrogen, coolin the calcium carbide resulting from the reducing operation, crushing the calcium phosphoric acid and calcium cyanamide carbide, and reheating the calcium carbide in the presence of the nitrogen producing calcium cyanamide.

13. Apparatus for producing phosphoric acid and calcium cyanamide comprising a reducing furnace for reducing phosphate rock with carbon, a condenser communicating with the reducing furnace adapted to receive the CO gas and volatile phosphorus from the reducing furnace and to condense the phosphorus and remove the CO therefrom, an oxldizing furnace communicating with the condenser, means for admitting air to the oxidizing furnace producing phosphoric acid and nitrogen, a cooler communicating with the oxidizing furnace, a precipitator communicating with the cooler, means for cooling and crushing the calcium carbide from the reducing furnace, a fixation furnace adapted to receive the calcium carbide from the cooling and crushing means and means for passing the nitrogen-from the precipitator into Tic its 

